Plasma-processing apparatus

ABSTRACT

A plasma-processing apparatus having a high frequency power application electrode in which a plasma is generated by supplying a VHF power to said high frequency power application electrode, characterized in that said plasma-processing apparatus has an impedance matching equipment comprising a capacitive element and an inductive element which are mutually connected in series connection and which is arranged such that said capacitive element and said inductive element of said impedance matching equipment are symmetrical to the center of said high frequency power application electrode.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a plasma-processing apparatus in which plasma discharge by means of a highs frequency power with a frequency belonging to a very high frequency (VHF) band region (this frequency will be hereinafter simply referred to as “VHF”) is used, including a plasma CVD apparatus or a plasma etching apparatus, which is used for the production of a semiconductor representatively such as an amorphous silicon series semiconductor, a crystalline silicon series semiconductor or the like.

[0003] 2. Related Background Art

[0004] There are known a number of plasma-processing apparatus in which plasma discharge by means of a high frequency power is used, including plasma CVD apparatus and plasma etching apparatus, wherein as said high frequency power, a high frequency power with a frequency of 13.56 MHz is generally used.

[0005] In general, such plasma-processing apparatus basically comprises has a vacuum chamber having a reaction space formed between a high frequency power application electrode and a counter electrode (an anode) and a high frequency power source which is connected to said high frequency power application electrode through a matching box and a power supply cable, wherein a high frequency power with a frequency of 13.56 MHz from the high frequency power source is supplied to the high frequency power application electrode and simultaneously with this, a gas is introduced into the reaction space, to cause discharge in the reaction space to produce a plasma in the reaction space, whereby an object to be plasma-processed such as a substrate which is arranged in the reaction space is plasma-processed by said plasma.

[0006] In the plasma-processing apparatus which is operated in this way, there is a tendency in that a capacitance formed between the high frequency power application electrode and the counter electrode (as an earth electrode) and that formed between the high frequency power application electrode and members (including the inner wall face of the vacuum chamber) with earth potential which are present in the peripheries of the high frequency power application electrode are together formed at the high frequency power application electrode. Further, in the case where an insulation member or the like which is made of ceramic is adopted in the electrode structure, there is an occasion in that a capacitance of a magnitude which cannot be disregarded is brought about at the high frequency power application electrode.

[0007] These capacitances become such that they are equivalently connected in parallel with the resistance of the plasma impedance to lower the value of the plasma impedance to afford a capacitive load. And this capacitive load makes to increase the transmitting current in the power transmission path, where Joule heat is occurred in the power supply cable and the like to increase the power loss in the high frequency power supplied to the high frequency power application electrode.

[0008] In order to solve such problem, there are several proposals. For instance, Japanese Laid-open Patent publication No. Hei 4(1992)-237940 (hereinafter referred to as “Document 1”) discloses a manner for diminishing such Joule heat occurred in the high frequency power transmission path. Particularly, Document 1 discloses a plasma generation apparatus having a vacuum vessel and a high frequency power application electrode provided in said vacuum vessel and which is connected to a high frequency power source through a power supply capable, wherein a plasma is generated in the vacuum vessel by virtue of a high frequency power supplied to the high frequency power application electrode through the power supply cable. In this plasma generation apparatus, as the means to cancel the capacitance of the plasma impedance and the capacitance which is formed between the high frequency power application electrode and the inner wall face of the vacuum chamber and the like which are with earth potential, separately from the power supply cable which is connected to the high frequency power application electrode, a variable-length coaxial pipe whose tip is short-circuited by a series resonance circuit comprising LC is connected to the high frequency power application electrode as a dielectric stub for the high frequency power application electrode.

[0009] Japanese Patent Publication No. Hei 1(1989)-19254 (hereinafter referred to as “Document 2”) discloses an electrode structure capable of diminishing the capacitance formed between the high frequency power application electrode and the members (including the inner wall face of the vacuum chamber) with earth potential) which are present in the peripheries of the high frequency power application electrode. Particularly, Document 2 discloses a plasma-processing apparatus provided with an electrode structure having a pair of plane parallel plate electrodes for the application of a high frequency power which are arranged to oppose to each other through a plasma generation region, one of said two plane parallel plate electrodes being grounded (earthed) to have earth potential, wherein at least one metal plate which is insulated from the non-earthed plate electrode and also from the conductors present in the peripheries of the non-earthed plate electrode is inserted to diminish the capacitance formed between the non-earthed plate electrode and the conductors present in the peripheries of the non-earthed plate electrode.

[0010] Document 2 describes that the electrode structure makes it possible to diminish the inter-electrode capacitance between the high frequency power application electrode and the conductors excluding the counter electrode and prevent occurrence of discharge and generation of a plasma at unnecessary portions.

[0011] By the way, in recent years, attempts have been made in order to achieve the formation of a non-crystalline (amorphous) silicon thin film or a crystalline silicon thin film on a substrate at an improved deposition rate using the plasma-processing apparatus in which a high frequency plasma generated by means of a high frequency power with a frequency of 13.56 MHz is used.

[0012] However, because the high frequency plasma generated by means of a high frequency power with a frequency of 13.56 MHz which belongs to a HF band region has a relatively small energy which is incapable of achieving a high deposition rate. In fact, the deposition rate which makes it possible to deposit a high quality non-crystalline silicon film or a high quality crystalline film on a substrate is several Angstroms (Å)/sec or less.

[0013] In order to more raise the deposition rate, it is necessary to increase the density of the plasma generated. For this purpose, it is necessary to apply a large high frequency power with a frequency belonging to a VHF (very high frequency) band region or a frequency band region greater than said VHF band region to the high frequency power application electrode of the plasma CVD apparatus.

[0014] Separately, in order to more improve the productivity of a large area semiconductor device such as a display or a solar cell in which a semiconductor comprising a crystalline silicon thin film or a non-crystalline silicon thin film is used and which excels in the quality and performance, it is necessary to uniformly deposit a crystalline silicon thin film or a non-crystalline silicon thin film which excels in the quality and property over a large area at an improved deposition rate.

[0015] For achieving this purpose, it is necessary to use a high frequency plasma whose energy is greater than that generated by means of a high frequency power with a frequency of 13.56 MHZ which belongs to a HF band region.

[0016] In this connection, various studies have been made in order to achieve high speed film formation over a large area using a plasma generated by means of a large high frequency power with a very high frequency (VHF) or a frequency belonging to a microwave band region. For this purpose, it is required that such large high frequency power is supplied uniformly to the entire region of a large high frequency power application electrode having a large area so as to generate a uniform plasma having a high density over a large area.

[0017] In the case where a deposited film is intended to form uniformly over a large area substrate using a plasma generated by means of such large high frequency power with, for instance, a VHF (this plasma will be hereinafter referred to as “VHF plasma”), it is necessitated that the high frequency power application electrode is enlarged to have a larger area than said large area substrate. In this case, when the technique described in Document 1 is adopted, such problems as will be described in the following are liable to entail. When a high frequency power with a VHF (hereinafter referred to as “VHF power”) is supplied to the high frequency power application electrode through the power supply cable, the Joule heat occurred in the high frequency power transmission path is increased to greatly increase the power loss and in addition to this, because the inductance component is excessively large, the electric field distribution at the face of the high frequency power application electrode becomes uneven, where a plasma is hardly generated. Thus, it is impossible to generate a uniform VHF plasma over a large area. In order to generate a uniform VHF plasma over a large area by means of a VHF power, it is necessary to consider that the VHF plasma has a larger energy than that generated by means of a high frequency power with a frequency of 13.56 MHz. In addition, the high frequency power application electrode through which a VHF power is supplied is necessary to be considered as a distributed constant circuit. Particularly, it is necessary to contrive the position for the VHF power to be supplied to the high frequency power application electrode. In addition, it is necessary to contrive an impedance matching equipment capable of effectively diminishing the capacitance of the high frequency power application electrode. It is also necessary contrive how the impedance matching equipment should structured and how the impedance matching equipment should be positioned to the high frequency power application electrode.

[0018] Unless these factors are contrived, it is difficult to stably and continuously generate a uniform VHF plasma such that it is uniformly distributed over a large area at a uniform density, where it is almost impossible to deposit a high quality film over a large area substrate at a uniform thickness and at a high deposition rate.

[0019] Thus, in accordance with the technique described in Document 1, it is difficult to stably and continuously generate a uniform VHF plasma over a large area at a uniform density so that a high quality film can be deposited uniformly over a large area substrate at a high deposition rate.

[0020] Separately, in the case where the high frequency power application electrode is enlarged to have a large area in order to make it possible to supply a VHF power which is a large high frequency power, the capacitance thereof is difficult to be sufficiently diminished in accordance with the technique described in Document 2, where problems are liable to entail in that particularly the power introduction portion of the high frequency power application electrode is overheated and the high frequency power application electrode is damaged.

[0021] Thus, in accordance with the technique described in Document 2, it is also difficult to stably and continuously generate a uniform VHF plasma over a large area at a uniform density so that a high quality film can be deposited uniformly over a large area substrate at a high deposition rate.

SUMMARY OF THE INVENTION

[0022] In view of the foregoing situations of the prior art, the present invention is aimed at providing a plasma-processing apparatus which enables to stably and continuously generate a uniform VHF plasma such that it is uniformly distributed over a large area at a uniform density and to form a high quality deposited film, which is highly functional and free of defect, over a large area substrate at a uniform thickness and at a high deposition rate.

[0023] Said functional deposited film includes a crystalline silicon series semiconductor film, a non-crystalline silicon series semiconductor film and the like.

[0024] Another object of the present invention is to provide a plasma-processing apparatus typically comprising a vacuum vessel having a reaction space formed between a high frequency power application electrode and an earth electrode which are arranged in said vacuum vessel such that they are opposed to each other, said high frequency power application electrode having a face exposed to said reaction space, wherein a VHF power is supplied to said high frequency power application electrode to generate a plasma in said reaction space, characterized in that between other face of said high frequency power application electrode excluding said face thereof exposed to said reaction space and a conductor with earth potential comprising at least part of the circumferential wall of said vacuum vessel, an impedance matching equipment comprising a capacitive element and an inductive element which mutually are connected in series connection is arranged such that each of said capacitive element and said inductive element of said impedance matching equipment becomes symmetrical to the center of said high frequency power application electrode. Here, said earth electrode comprises an electrically conductive member comprising an object to be plasma-processed such as a substrate on which a film is to be deposited.

[0025] Said impedance matching equipment is preferred to be designed such that a conductor plate which is insulated from said high frequency power application electrode in terms of direct current potential is arranged in parallel to said opposite face of said high frequency power application electrode and said inductive element is inserted between said conductor plate and said conductor with earth potential.

[0026] In this case, said conductor plate pays a role to function as aforesaid capacitive element in relation to said high frequency power application electrode

[0027] It is possible to make such that the side of the opposite face of said high frequency power application electrode which is not faced to the reaction space is atmospheric pressure and said impedance matching equipment is arranged in series between said opposite face of said high frequency power application electrode and said conductor with earth potential.

[0028] It is preferred to make said impedance matching equipment such that it is movable in parallel to said high frequency power application electrode.

[0029] It is possible that said impedance matching equipment comprises a plurality of units comprising a capacitive element and an inductive element which are connected in series connection.

[0030] The plasma-processing apparatus of the present invention which is constituted as above described has significant advantages such that a uniform VHF plasma is stably and continuously generated such that it is uniformly distributed in the entire region of the reaction space at a uniform density and because of this, a high quality deposited film, which is highly functional and free of defect, is formed over the entire surface of a large area substrate at a uniform thickness and at a high deposition rate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a schematic diagram illustrating the constitution of a first example of a plasma-processing apparatus of the present invention.

[0032]FIG. 2 is a schematic diagram illustrating the constitution of a second example of a plasma-processing apparatus of the present invention.

[0033]FIG. 3 is a schematic diagram illustrating the constitution of a third example of a plasma-processing apparatus of the present invention.

[0034]FIG. 4 is a schematic diagram illustrating the constitution of a fourth example of a plasma-processing apparatus of the present invention.

[0035] FIGS. 5(a) and 5(b) are schematic diagrams respectively illustrating an example of an earthed electrode comprising a substrate or a substrate retaining member used in any of the plasma-processing apparatus shown in FIGS. 1 to 4.

[0036] FIGS. 6(a) and 6(b) are schematic diagrams for explaining the operation and constitution of the impedance matching equipment in the plasma-processing apparatus shown in FIG. 1.

[0037]FIG. 7 is a schematic diagrams for explaining the constitution of the impedance matching equipment in the plasma-processing apparatus shown in FIG. 3.

[0038]FIG. 8 is a graph showing plasma emission intensity distributions in Example 1 which will be described later.

[0039]FIG. 9 is a graph showing plasma emission intensity distributions in Example 2 which will be described later.

[0040]FIG. 10 is a graph showing deposition rate distributions of amorphous silicon films in Example 3 which will be described later.

[0041]FIG. 11 is a graph showing deposition rate distributions of amorphous silicon films in Comparative Example 1 which will be described later.

DESCRITION OF THE INVENTION AND PREFERRED EMBODIMENTS

[0042] The present invention achieves the foregoing objects, and provides a plasma-processing apparatus typically comprising a vacuum vessel having a reaction space formed between a high frequency power application electrode and an earth electrode which are arranged in said vacuum vessel such that they are opposed to each other, said high frequency power application electrode having a face exposed to said reaction space, wherein a VHF power is supplied to said high frequency power application electrode to generate a plasma in said reaction space, characterized in that between other face of said high frequency power application electrode excluding said face thereof exposed to said reaction space and a conductor with earth potential comprising at least part of the circumferential wall of said vacuum vessel, an impedance matching equipment comprising a capacitive element and an inductive element which are mutually connected in series connection is arranged such that each of said capacitive element and said inductive element of said impedance matching equipment becomes symmetrical to the center of said high frequency power application electrode. Said earth electrode comprises an electrically conductive member as an object to be plasma-processed such as a substrate on which a film is to be deposited.

[0043] In the following, the present invention will be described in more detail with reference to the drawings.

[0044]FIG. 1 is a schematic diagram illustrating the constitution of a first example of a plasma-processing apparatus of the present invention. FIG. 2 is a schematic diagram illustrating the constitution of a second example of a plasma-processing apparatus of the present invention. FIG. 3 is a schematic diagram illustrating the constitution of a third example of a plasma-processing apparatus of the present invention. FIG. 4 is a schematic diagram illustrating the constitution of a fourth example of a plasma-processing apparatus of the present invention. FIGS. 5(a) and 5(b) are schematic diagrams respectively illustrating an example of an earthed electrode comprising a substrate or a substrate retaining member used in any of the plasma-processing apparatus shown in FIGS. 1 to 4. FIGS. 6(a) and 6(b) are schematic diagrams for explaining the operation and constitution of the impedance matching equipment in the plasma-processing apparatus shown in FIG. 1. FIG. 7 is a schematic diagrams for explaining the constitution of the matching equipment in the plasma-processing apparatus shown in FIG. 3.

[0045] In FIGS. 1 to 7, reference numeral 1 indicates a vacuum vessel, reference numeral 2 an earthed electrode comprising a substrate or a substrate retaining member [see, FIGS. 5(a) and 5(b)], reference numeral 3 a high frequency power application electrode, reference numeral 4 an electric heater, reference numeral 5 a conductor plate which functions as a capacitive element 5′, reference numeral 6 an inductive element, reference numeral 7 an impedance matching equipment, reference numeral 8 an exhaust pipe, reference numeral 9 a shield case, reference numeral 10 a matching box, reference numeral 11 a high frequency power source capable of supplying a VHF power, reference numeral 12 a reaction space, reference numeral 13 a gas spouting hole, reference numeral 14 a metal fixture, reference numeral 15 an insulator, reference numeral 16 a shield pipe, reference numeral 17 an insulator, and reference numeral 18 a gas introduction pipe extending from a gas supply system (not shown).

[0046] The high frequency power application electrode 3 is shaped in a plate form whose inside is hallowed and which is provided with a plurality of gas spouting holes 13 at the face thereof which is exposed to the reaction space 12. The gas introduction pipe 18 is connected to the high frequency power application electrode 3 to open into the hallow space thereof. Gas is introduced into the hallow space of the high frequency power application electrode 3 through the gas introduction pipe 18 and the gas introduced in this way is spouted into the reaction space 13 though the gas spouting holes 13.

[0047] The high frequency power application electrode 3 functions to supply a VHF power which is transmitted thereto from the high frequency power source 11 through the matching box 10 into the reaction space 12, where discharge is occurred to decompose the gas introduced into the reaction space 12 thereby to generate a plasma in the reaction space 12.

[0048] The exhaust pipe 8 is communicated with the inside of the reaction space 12. The exhaust pipe 8 is provided with a control valve (not shown) and is connected to a vacuum pump (not shown). The exhaust pipe 8 serves to exhaust the gas in the reaction space 12 by means of the vacuum pump (not shown) connected thereto while adjusting the gaseous pressure in the inside of the reaction space 12 by means of the control valve (not shown) provided at the exhaust pipe 8.

[0049] Now, detailed description will be made of the plasma-processing apparatus shown in FIGS. 1 and 2.

[0050] In each of the plasma-processing apparatus shown in FIGS. 1 and 2, the vacuum vessel 1 has the high frequency power application electrode 3 shaped in a plate form and the earthed electrode 2 which are arranged therein such that they are opposed to each other so as to establish the reaction space 12 between them. The clearances present between the high frequency power application electrode 3 and the circumferential wall of the vacuum vessel 1 are hermetically sealed so that the inside space including the reaction space 12 and which is circumscribed by the circumferential wall of the vacuum vessel 1 and the high frequency power application electrode 3 is kept in an air-tight state, where the side of the rear face of the high frequency power application electrode 3 which is opposite to the face thereof exposed to the reaction space 12 is situated on an atmospheric pressure side.

[0051] The high frequency power source 11 is electrically connected to the center of the rear face of the high frequency power application electrode 3 through the matching box 10 so that a VHF power from the high frequency power source 11 is supplied to the center of the high frequency power application electrode 3, followed by being supplied into the reaction space 12.

[0052] On the side of the rear face of the high frequency power application electrode 3, an impedance matching equipment 7 is arranged.

[0053] In the embodiment shown in FIG. 1, the impedance matching equipment 7 comprises a conductor plate 5 and four inductive elements 6 which are arranged such that the conductor plate 5 is held by the four inductive elements 6 arranged in parallel to each other in a longitudinal direction, where the four inductive elements 6 are connected to the conductor plate 5 respectively in series connection.

[0054] And the impedance matching equipment 7 is arranged such that not only the conductor plate 5 but also the four inductive elements 6 respectively become symmetrical to the center of the high frequency power application electrode 3, where the conductor plate 5 pays a role to function as a capacitive element 5′ in relation to the high frequency power application electrode 3.

[0055] It is preferred that the conductor plate 5 is arranged substantially in parallel to the high frequency power application electrode 3. However, the conductor plate 5 is not always necessary to be arranged such that it is in parallel to the high frequency power application electrode 3. The conductor plate 5 may be arranged in other appropriate arrangement manner to the high frequency power application electrode 3.

[0056] On the side of the rear face of the high frequency power application electrode 3, the shield case 9 is provided to enclose the space where the impedance matching equipment 7 is arranged, so that VHF power released from the rear side of the high frequency power application electrode 3 is confined within the space enclosed by the shield case. The shield case 9 is provided with four holes which allow the four inductive elements 6 to pass through so as to move up and down by means of a driving motor (not shown). At an external portion of each of the four holes of the shield case 9, a metal fixture 14 is provided so as to electrically ground the shield case 9 and each inductive element 6.

[0057] Similarly, in the embodiment shown in FIG. 2, the impedance matching equipment 7 comprises two units respectively arranged on each of the opposite sides with respect to the center of the high frequency power application electrode 3. Each unit comprises a conductor plate 5 and two inductive elements 6 which are arranged such that the conductor plate 5 is held by the two inductive elements 6 arranged in parallel to each other in a longitudinal direction, where each of the two inductive elements 6 is connected to the conductor plate 5 in series connection. And each unit as the impedance matching equipment 7 is arranged such that not only the conductor plate 5 but also the two inductive elements 6 respectively become symmetrical to the center of the high frequency power application electrode 3, where the conductor plate 5 pays a role to function as a capacitive element 5′ in relation to the high frequency power application electrode 3. In this case, it is also preferred that the conductor plate 5 is arranged substantially in parallel to the high frequency power application electrode 3.

[0058] As well as in the embodiment shown in FIG. 1, on the side of the rear face of the high frequency power application electrode 3, the shield case 9 is provided to enclose the space where the impedance matching equipment 7 comprising aforesaid two units is arranged, so that VHF power released from the rear side of the high frequency power application electrode 3 is confined within the space enclosed by the shield case. The shield case 9 is provided with four holes which allow the four inductive elements 6 of the two units to pass through so as to move up and down by means of a driving motor (not shown). At an external portion of each of the four holes of the shield case 9, a metal fixture 14 is provided so as to electrically ground the shield case 9 and each inductive element 6.

[0059] It is possible that the impedance matching equipment 7 comprises a number of units having such configuration as above described. In this case, the impedance of the high frequency application electrode 3 can be more finely matched.

[0060] In the following, description will be made of an embodiment of the operation and constitution of the impedance matching equipment used in the plasma-processing apparatus of the present invention with reference to FIGS. 6(a) and 6(b).

[0061]FIG. 6(a) is a schematic diagrams for explaining the operation of the impedance matching equipment in the plasma-processing apparatus shown in FIG. 1. FIG. 6(b) is a schematic diagram for detailing of the impedance matching equipment shown in FIG. 6(a), where an upper figure is a schematic elevation view of the impedance matching equipment and a lower figure is a schematic underside view of the impedance matching equipment.

[0062]FIG. 6(a) shows an embodiment when the impedance matching equipment 7 arranged on the side of the rear face of the high frequency power application electrode 3 is moved down by means of the driving motor (not shown). FIG. 6(b) details the constitution of the impedance matching equipment 7.

[0063] Now, as FIG. 6(b) illustrates, the impedance matching equipment 7 comprising the conductor plate 5 (which is arranged substantially in parallel to the high frequency power application electrode 3) and the four inductive elements 6 shaped in a bar-like form (which are arranged in parallel to each other and are collected to the conductor plate 5 in series connection) is arranged on the side of the rear face of the high frequency power application electrode 3, where capacitive coupling is established between the conductor plate 5 and the high frequency power application electrode 3, whereby the conductor plate 5 is made to function as a capacitive element 5′. The capacitance of the capacitive element 5′ is decided depending on the interval between the conductor plate 5 and the high frequency power application electrode 3. The opposite end portions of the four inductive elements 6 are fastened by passing them through the four holes of the shield case 9, where the joining portions of the opposite end portions of the inductive elements 6 with the shield case 9 are short-circuited by electrically grounding the joining portions by means of the metal fixtures 14, where the inductance of the inductive elements 6 is decided depending on the length L of the inductive elements 6 between the conductor plate 5 and the short-circuited joining portions of the inductive elements 6 with the shield case 9.

[0064] Because a VHF power from the high frequency power source is applied to the center of the rear face of the high frequency power application electrode 3, the impedance matching equipment 7 is arranged such that it becomes symmetrical to the center of the high frequency power application electrode 3. When the impedance matching equipment 7 is moved up or down, in accordance with the movement of the impedance matching equipment 7, the capacitance of the capacitive element 5′ and the inductance of the inductive element 6 are changed.

[0065] In the case where from the side of the matching box 10, the impedance matching equipment 7 is considered as an electric circuit, it can be said that the impedance matching equipment 7 is connected with the capacitance of the high frequency power application electrode 3 in parallel connection to form a parallel resonance circuit with the capacitance of the high frequency power application electrode 3. Thus, it is considered that by moving the impedance matching equipment 7 up or down so as to match with a parallel resonance point, the capacitance of the high frequency power application electrode 3 is cancelled so that it can be regarded as a resistance of infinity. In this connection, it is considered that the impedance of the high frequency power application electrode 3 becomes to be a resistance component substantially due to a plasma generated in the reaction space and therefore, the reactive current of the high frequency power application electrode 3 is decreased and the joule loss in the power supply path from the matching box 10 to the high frequency power application electrode 3 is diminished.

[0066] Here, in the case where a VHF power is supplied to the high frequency power application electrode 3, because the high frequency power application electrode is considered as a distributed constant circuit, when the impedance matching equipment 7 is arranged such that it is asymmetrical to the center of the high frequency power application electrode 3, the VHF power is supplied such that it is localized at the face of the high frequency power application electrode 3. Therefore, by arranging the impedance matching equipment 7 such that it is symmetrical to the center of the high frequency power application electrode 3, it is possible to prevent the capacitance of the high frequency power application electrode from being localized.

[0067] Now, in the plasma-processing apparatus shown in FIG. 6(a) (which is corresponding to FIG. 1), desired gas is supplied into the high frequency power application electrode 3 (which is a plate form whose inside is hallowed as previously described) through the gas introduction pipe 18 and the gas thus introduced into the high frequency power application electrode 3 is supplied into the reaction space 12 through the spouting holes 13 provided at the high frequency power application electrode 3. Simultaneously with this, a VHF power from the high frequency power source is supplied to the center VHF power from the high frequency power source 11 is supplied to the high frequency power application electrode 3 from the center of the rear face thereof, followed by being supplied into the reaction space 12, whereby a plasma is generated in the reaction space. In this case, the impedance of the high frequency power application electrode 3 is adjusted by changing the position of the impedance matching equipment 7 by moving the impedance matching equipment up or down as shown in FIG. 6(a), so that the emission intensity of the plasma generated in the reaction space 12 is increased. The exhaustion of gas from the reaction space is performed through the exhaust pipe 8.

[0068] In the above, the introduction of gas into the reaction space is carried out though the gas spouting holes of the high frequency power application electrode. However this is not limitative. It is possible to introduce said gas into the reaction space from a peripheral portion of the reaction space.

[0069] In the case where it is intended to form a deposited film, by using a film-forming gas as the gas to be supply into the reaction space and using a metallic substrate as the earth electrode 2 as shown in FIG. 5(a) or a substrate retaining member made of a metallic material having a glass substrate retained thereon as shown in FIG. 5(b) as the earth electrode 2, said deposited film can be formed on said metallic substrate or said glass substrate. In this case, the film formation is carried out by adjusting the position of the impedance matching equipment 7 with reference to the thickness distribution of the deposited film formed on the substrate as the earth electrode.

[0070] Separately, in the case where it is intended to subject a given member to an plasma-etching treatment, by using an etching raw material gas as the gas to be supply into the reaction space and using said member as it is as the earth electrode 2 when said member is electrically conductive or a substrate retaining member made of a metallic material having said member retained thereon as shown in FIG. 5(b) as the earth electrode 2 when said member is not electrically conductive, the surface of said member can be plasma-etched. In this case, the etching treatment is carried out by adjusting the position of the impedance matching equipment 7 with reference to the etched state of the member as the earth electrode.

[0071] Now, in the plasma-processing apparatus shown in FIGS. 1 and 2, the rear face side of the high frequency power application electrode 3 is situated in an atmosphere of atmospheric pressure and there is a spacing between the high frequency power application electrode and the impedance matching equipment 7. Therefore, no abnormal discharge is occurred between the high frequency power application electrode 3 and the impedance matching equipment 7 and also between the impedance matching equipment 7 and the shield case 9.

[0072] Description will be made of the plasma-processing apparatus shown in FIGS. 3 and 4.

[0073] Each of the plasma-processing apparatus shown in FIGS. 3 and 4 is a partial modification of the plasma-processing apparatus shown in FIG. 1 in that the high frequency power application electrode 3 is entirely situated in a reduced pressure atmosphere. Particularly, in each of the plasma-processing apparatus shown in FIGS. 3 and 4, the clearances present between the conductor plate 5 of the impedance matching equipment 7, the high frequency power application electrode 3 and the wall of the shield case 9 are filled with an insulating material 17, where the conductor plate 5 is insulated from the high frequency power application electrode 3 through the insulating material 17 provided between them.

[0074] And in the plasma-processing apparatus shown in FIG. 3, the impedance matching equipment 7 comprising the conductor plate 5 (which functions as a capacitive element 5′ in relation to the high frequency power application electrode 3) and the four inductive elements 6 shaped in a bar-like form which are connected to the conductor plate 5 in series connection is arranged on the side of the rear face of the high frequency power application electrode 3 as well as in the case of the plasma-processing apparatus shown in FIG. 1.

[0075] In the plasma-processing apparatus shown in FIG. 3, each inductive element 6 has a first portion which is situated in the inside of the shield case 9 which is filled with the insulating material 17 and a second portion which inserted in a double-structured shield pipe 16 comprising a non-movable inner pipe and an outer pipe capable of being slidably moved and which is provided to hermetically penetrate the circumferential wall of the vacuum vessel 1 so as to project outside the vacuum vessel 1, where the clearance between the part of said second portion which is situated in the inner pipe of the shield pipe 16 and said inner pipe is filled with an extended portion of the insulating material 17 filled in the inside of the shield case 9, and an end portion of the second portion of the inductive element 6 is short-circuited by electrically grounding by means of the metal fixture 14 fixed to the shield pipe 16 as shown in FIG. 3. Aforesaid clearance is not always necessary to be filled with the insulating material 17. That is, in the case where the clearance between the inner pipe and the second portion of the inductive element 6 is made to be less than 3 mm where no discharge is occurred, it is not necessary for the clearance to be filled with the insulating material 17.

[0076] In the plasma-processing apparatus shown in FIG. 4, the impedance matching equipment 7 comprising the conductor plate 5 (which functions as a capacitive element 5′ in relation to the high frequency power application electrode 3) and the one inductive element 6 shaped in a bar-like form which is connected to the conductor plate 5 in series connection is arranged at each of the opposite end sides of the high frequency power application electrode 3.

[0077] In the plasma-processing apparatus shown in FIG. 4, each inductive element 6 has a first portion which is situated in the inside of the shield case 9 which is filled with the insulating material 17 and a second portion which inserted in a double-structured shield pipe 16 comprising a non-movable inner pipe and an outer pipe capable of being slidably moved and which is provided to hermetically penetrate the circumferential wall of the vacuum vessel 1 so as to project outside the vacuum vessel 1, where the clearance between the part of said second portion which is situated in the inner pipe of the shield pipe 16 and said inner pipe is filled with an extended portion of the insulating material 17 filled in the inside of the shield case 9, and an end portion of the second portion of the inductive element 6 is short-circuited by electrically grounding by means of the metal fixture 14 fixed to the shield pipe 16 as shown in FIG. 4. Aforesaid clearance is not always necessary to be filled with the insulating material 17. That is, in the case where the clearance between the inner pipe and the second portion of the inductive element 6 is made to be less than 3 mm where no discharge is occurred, it is not necessary for the clearance to be filled with the insulating material 17.

[0078] With reference to FIG. 8, the impedance matching equipment 7 in the plasma-processing apparatus shown in FIG. 3 will be detailed.

[0079] Capacitive coupling is established between the high frequency power application electrode 3 and the conductor plate 5 which is arranged substantially in parallel to the high frequency power application electrode 3, whereby the conductor plate 5 becomes to function as a capacitive element 5′, and where the inductive element 6 is connected to the conductor plate 5 in series connection. For the double-structured shield pipe 16, one end portion of the outer pipe thereof is short-circuited with the inner pipe thereof which is electrically grounded by means of a spring plate and the other end portion of the outer pipe is short-circuited with the inductive element 6 by way of electrical grounding by means of a spring plate. By slidably moving the outer pipe up or down, the length L of the inductive element is changed, whereby the inductance of the inductive element 6 is adjusted. Here, the clearances present between the conductor plate 5 of the impedance matching equipment 7, the high frequency power application electrode 3 and the wall of the shield case 9 are filled with the insulating material 17. And the clearance present between the inductive element 6 and the inner pipe of the double-structured shield pipe 16 is also filled with the insulating material 17 as shown in FIG. 7.

[0080] By doing in the way as above described, it is possible to match the impedance of the high frequency power application electrode 3 so as to cancel the conductive component of the high frequency power application electrode. This makes it possible that the VHF power supplied to the high frequency power application electrode 3 is effectively and evenly supplied into the reaction space 12 where a high density plasma is uniformly generated therein, without occurrence of problems such as abnormal discharge, overheat, and breakage at the power supply portion and the like of the high frequency power application electrode.

[0081] And it is possible to efficiently form a high quality deposited film having a uniform thickness over a large area at a high deposition rate by adjusting the frequency of a high frequency power supplied to the high frequency power application electrode, the internal gas pressure of the reaction space, the interval between the high frequency power application electrode and the counter electrode (the earth electrode), and the flow rate of the gas introduced into the reaction space.

[0082] In the following, description will be made of the findings obtained by the present inventors through experiments in the course to have completed the present invention.

[0083] In order that the density of a plasma generated is increased to achieve a high deposition rate for a film deposited, it is necessitated that a high frequency power with a frequency belonging to a VHF band region (that is, a VHF power) is supplied to a film-forming raw material gas introduced in the discharge space (the reaction space) through the high frequency power application electrode to decompose the raw material gas whereby producing a large amount of radicals.

[0084] Now, using a plasma-processing apparatus structured in the same way as in FIG. 1, the present inventors examined emission intensity of plasma generated in the plasma generation region (that is, the reaction space) of said plasma-processing apparatus.

[0085] Said plasma-processing apparatus has a vacuum vessel (1) having a reaction space (12) formed between a high frequency power application electrode (3) and an earth electrode (2) which are arranged in said vacuum vessel such that they are opposed to each other; said high frequency power application electrode (3) having a face exposed to said reaction space; said vacuum vessel further having an impedance matching equipment (7) on the side of the rear face of said high frequency power application electrode (3) which is exposed to an atmospheric pressure atmosphere reaction space (12) such that said impedance matching equipment (7) is arranged between said high frequency power application electrode (3) and a shield case (9) provided so as to shield the space including said impedance matching equipment (7) arranged therein, such that the impedance of said high frequency power application electrode (3) becomes symmetrical to the center of said high frequency power application electrode; said impedance matching equipment (7) comprising a conductor plate (5) and four inductive elements (6) shaped in a bar-like form which are connected with said conductor plate (5) in series connection, wherein said conductor plate (5) of said impedance matching equipment (7) is arranged substantially in parallel to said high frequency power application electrode (3) such that said conductor plate (5) extends along substantially the entire region of the rear face of said high frequency power application electrode (3) so as to establish capacitive coupling with said high frequency power application electrode (3) where said conductor plate functions as a capacitive element (5′), and the opposite end portions of said four inductive elements (6) of said impedance matching equipment (7) are electrically grounded through said shield case (9) and by means of metal fixtures 14.

[0086] The emission intensity of plasma generated in the reaction space (12) was measure from the face of the earth electrode (2) which is exposed to the reaction space (12) using an optical fiber and a plasma emission spectrometer.

[0087] As a result, there were obtained findings as will be described below.

[0088] The constant of the capacitive element (5′) formed between the high frequency power application electrode (3) and the conductor plate (5) to the inductive element (6) was adjusted to given values by moving the impedance matching equipment (7) arranged between the high frequency power application electrode (3) and the shield case (9) up and down, where the emission intensity of plasma generated in the reaction space (12) was examined with respect to each of the adjusted values.

[0089] As a result, there was obtained a finding that the emission intensity of plasma generated in the reaction space is increased and it becomes uniform when the constant of the capacitive element (5′) to the inductive element (6) is adjusted in the way as above described.

[0090] For the reason for this, the present inventors considered such that the front face of the high frequency power application electrode (3) have a resistance component and that the high frequency power application electrode (3) functions as a distributed constant circuit having a capacitive component and an inductive component in parallel.

[0091] Based on this thought, the present inventors conducted examination by making the position where the capacitive element (5′) and the inductive element (6) which are connected in series connection are arranged to be asymmetrical to the center of the high frequency power application electrode (3).

[0092] As a result, there was obtained a finding that the electric current flown in the high frequency power application electrode (3) becomes uneven and this is influenced to the uniformity of plasma generated in the reaction space (12).

[0093] Taking the above findings into consideration, the present inventors contrived a plasma-processing apparatus comprising a vacuum vessel having a reaction space formed between a high frequency power application electrode shaped in a plate form and an earth electrode which are arranged in said vacuum vessel such that they are opposed to each other, said high frequency power application electrode having a face exposed to said reaction space, wherein between other face of said high frequency power application electrode excluding said face thereof exposed to said reaction space and a conductor with earth potential comprising at least part of the circumferential wall of said vacuum vessel, an impedance matching equipment comprising a capacitive element and an inductive element which mutually are connected in series connection is arranged such that each of said capacitive element and said inductive element of said impedance matching equipment becomes symmetrical to the center of said high frequency power application electrode.

[0094] This plasma-processing apparatus was found to have such advantages as will be described below.

[0095] By adjusting the position of the impedance matching equipment in an upward or downward direction, it is possible that a parallel resonance between the capacitive component of the high frequency power allocation electrode and the inductive component of the impedance matching equipment. This greatly diminishes the reactive current flown between the high frequency power application electrode and a matching box which is electrically connected to a high frequency power source and also to the high frequency power application electrode. This makes it possible to uniformly supply a large high frequency power with a frequency belonging to a VHF band region (that is, a VHF power) the entire face of the high frequency power application electrode which is faced to the reaction space so that the VHF power is uniformly supplied to raw material gas introduced in the reaction space or a plasma generated in the reaction space, whereby a plasma having a high density is uniformly generated in the entire region of the reaction space.

[0096] Because a plasma having a high density is uniformly generated in the reaction space as above described, a high quality deposited film is formed over the entire surface of a substrate which functions as the earth electrode at a uniform thickness and at a high deposition rate.

[0097] The present invention also provides a method of forming a deposited film using aforesaid plasma-processing apparatus. It is a matter of course that this method is effective in forming a deposited film using a high frequency power with a frequency of 13.56 MHz. However, this method is significantly effective particularly in the case of forming a deposited film using a VHF power.

[0098] Specifically, as above described, by adopting the constitution in the plasma-processing apparatus in that between other face of the high frequency power application electrode excluding the face thereof exposed to the reaction space and the conductor with earth potential comprising at least part of the circumferential wall of the vacuum vessel, the impedance matching equipment comprising the capacitive element and the inductive element which are mutually connected in series connection is arranged such that each of the capacitive element and the inductive element of the impedance matching equipment becomes symmetrical to the center of the high frequency power application electrode, a plasma having a high density is uniformly generated in the entire region of the reaction space even when the reaction space has a large area. Further in the case where a large high frequency power (that is, a VHF power) to the high frequency power application electrode of the conventional plasma-processing apparatus, the dielectric loss is significant. However, in the plasma-processing apparatus of the present invention, such dielectric loss is greatly diminished. Because of this, even when a large high frequency power, namely, a VHF power is used, it possible to realize the generation of a large power plasma.

[0099] Separately, in the case where film formation is performed by the plasma-processing apparatus of the present invention using a VHF power, it is possible to realize high speed film formation in a large area reaction space, where a high quality large area non-crystalline or crystalline silicon deposited film having greatly improved properties can be formed at a satisfactorily high deposition rate.

[0100] Besides, the plasma-processing apparatus can be used as a sputtering apparatus or an etching apparatus, where a large area member can be efficiently plasma-processed.

[0101] In the following, the present invention will be described in more detail with reference to examples. It should be understood that these examples are only for illustrative purposes and the scope of the present invention is not restricted by these examples.

EXAMPLE 1

[0102] In this example, description will be made of the state of plasma generated in the plasma-processing apparatus shown in FIG. 1.

[0103] In the plasma-processing apparatus shown in FIG. 1, as previously explained, the high frequency power application electrode 3 is arranged such that the front face thereof is exposed to the reaction space 12 which is formed between said front face and the earth electrode 2 arranged to oppose the high frequency power application electrode 3 and the rear face thereof is exposed to an atmosphere of atmospheric pressure. The atmospheric pressure side of the rear face of the high frequency power application electrode 3 is enclosed by the shield case 9.

[0104] In the space enclosed by the shield case 9, the impedance matching equipment 7 comprising one conductor plate 5 shaped in a plate form and four inductive elements 6 shaped in a bar form which are connected to the conductor plate 5 in series connection is arranged such that the conductor plate 5 and the four inductive elements 6 are symmetrical to the center of the rear face of the high frequency power application electrode 3.

[0105] Particularly, the conductor plate 5 is arranged substantially in parallel to the high frequency power application electrode 3, where the conductor plate 5 functions as a capacitive element 5′ in relation to the high frequency power application electrode 3. Each of the four inductive elements 6 comprises a bar-shaped inductive element whose diameter is 16 mm, and these four inductive elements 6 are arranged such that they are symmetrical to the center of the conductor plate 5, where their one ends are connected with the conductor plate 5 so as to retain the conductor plate 5 from the backside thereof. To be more specific, two of the four inductive elements are arranged on each of the opposite sides with respect to the center of the conductor plate 5.

[0106] The other end portions of the four inductive elements 6 thus arranged are made to penetrate through the four holes provided at the shield case 9, where they are electrically grounded by means of the metal fixtures 14 provided at the four holes of the shield case 9 to establish parallel connection with the capacitive component of the high frequency power application electrode 3.

[0107] Here, by moving the impedance matching equipment 7 constituted as above described in a upward or downward direction, it is possible to make such that the impedance value is changed so as to occur a parallel resonance with the capacitive component of the high frequency power application electrode 3.

[0108] Now, using the plasma-processing apparatus shown in FIG. 1 which is constituted as above described, the generation of plasma and the distribution of the plasma were observed as will be described below.

[0109] The size of the reaction space 12 was made to be 540 mm×890 mm, and the size of the high frequency power application electrode 3 was made to be 500 mm×850 mm.

[0110] H₂ gas was introduced into the reaction space at a flow rate of 1000 sccm through the spouting holes 13 of the high frequency power application electrode 3, and the inner pressure (the gas pressure) in the reaction space 12 was maintained at 266 Pa. Then, a VHF power with a frequency of 60 MHz having a wattage of 3 KW was supplied to the high frequency power application electrode 3, followed by being supplied into the reaction space, whereby plasma was generated in the reaction space 12. The emission intensity of the plasma generated in the reaction space 12 and the distribution thereof were examined at 15 points over the surface of the earth electrode 12 which is faced to the reaction space by means of a plasma emission spectrometer MAX 3000 produced by ATAGOBUSSAN Kabushiki Kaisha.

[0111] The examined results obtained are graphically shown in FIG. 8. In FIG. 8, the axis of abscissas indicates positions of the high frequency power application electrode and the axis of ordinates indicates emission intensities of plasma generated. (0, 0) of the coordinate (X, Y) corresponds to the center position of the high frequency power application electrode.

[0112] Based on the results shown in FIG. 8, it was found that the distributions of the plasma emission intensities are of a variation of ±10%. This means that substantially uniform and stable plasma having a strong emission intensity is obtained in the entire region of the reaction space. Separately, neither overheat at the power introduction portion of the high frequency power application electrode nor abnormal discharge were occurred during the plasma generation.

EXAMPLE 2

[0113] In this example, description will be made of the state of plasma generated in the plasma-processing apparatus shown in FIG. 3.

[0114] As previously described, the plasma-processing apparatus shown in FIG. 3 is a partial modification of the plasma-processing apparatus shown in FIG. 1 in that the high frequency power application electrode 3 is entirely situated in a reduced pressure atmosphere. Particularly, in the plasma-processing apparatus shown in FIG. 3, the clearances present between the conductor plate 5 of the impedance matching equipment 7, the high frequency power application electrode 3 and the wall of the shield case 9 are filled with an insulating material 17, where the conductor plate 5 is insulated from the high frequency power application electrode 3 through the insulating material 17 provided between them. The impedance matching equipment 7 is arranged on the side of the rear face of the high frequency power application electrode 3 as well as in the case of the plasma-processing apparatus shown in FIG. 1. The impedance matching equipment 7 comprises one conductor plate 5 shaped in a plate form and four inductive elements 6 shaped in a bar form which are connected to the conductor plate 5 in series connection is arranged such that the conductor plate 5 and the four inductive elements 6 are symmetrical to the center of the rear face of the high frequency power application electrode 3.

[0115] Particularly, the conductor plate 5 is arranged substantially in parallel to the high frequency power application electrode 3, where the conductor plate 5 functions as a capacitive element 5′ in relation to the high frequency power application electrode 3. Each of the four inductive elements 6 comprises a bar-shaped inductive element whose diameter is 16 mm, and these four inductive elements 6 are arranged such that they are symmetrical to the center of the conductor plate 5, where their one ends are connected with the conductor plate 5 so as to retain the conductor plate 5 from the backside thereof. And two of the four inductive elements are arranged on each of the opposite sides with respect to the center of the conductor plate 5. For the four inductive elements, it is made such that their impedance can be adjusted by ascending or descending the outer pipes of the double-structured shield pipes 16 outside the vacuum vessel 1, as previously described.

[0116] Now, using the plasma-processing apparatus shown in FIG. 3 which is constituted as above described, the generation of plasma and the distribution of the plasma were observed as will be described below.

[0117] The size of the reaction space 12 was made to be 510 mm×510 mm, and the size of the high frequency power application electrode 3 was made to be 500 mm×850 mm. And the interval between the earth electrode 2 and the high frequency power application electrode 3 which are mutually opposed through the reaction space 12 was made to be 10 mm.

[0118] H₂ gas was introduced into the reaction space at a flow rate of 1000 sccm through the spouting holes 13 of the high frequency power application electrode 3, and the inner pressure (the gas pressure) in the reaction space 12 was maintained at 133 Pa. Then, a VHF power with a frequency of 100 MHz having a wattage of 3 KW was supplied to the high frequency power application electrode 3, followed by being supplied into the reaction space, whereby plasma was generated in the reaction space 12. The emission intensity of the plasma generated in the reaction space 12 and the distribution thereof were examined at 9 points over the surface of the earth electrode 12 which is faced to the reaction space by means of a plasma emission spectrometer MAX 3000 produced by ATAGOBUSSAN Kabushiki Kaisha.

[0119] The examined results obtained are graphically shown in FIG. 9. In FIG. 9, the axis of abscissas indicates positions of the high frequency power application electrode and the axis of ordinates indicates emission intensities of plasma generated. And (0, 0) of the coordinate (X, Y) corresponds the center position of the high frequency power application electrode.

[0120] Based on the results shown in FIG. 9, it was found that the distributions of the plasma emission intensities are of a variation of ±6%. This means that substantially uniform and stable plasma having a strong emission intensity is obtained in the entire region of the reaction space. Separately, neither overheat at the power introduction portion of the high frequency power application electrode nor abnormal discharge were occurred during the plasma generation.

EXAMPLE 3

[0121] In this example, using the plasma-processing apparatus shown in FIG. 1 whose constitution is substantially the same as that in Example 1 except for using a substrate retaining member made of a metallic material and having such configuration as shown in FIG. 5(b) as the earth electrode 2, an amorphous silicon film was formed on a substrate [2′, see FIG. 5(b)] comprising a 7059 glass plate (produced by Corning Company) retained by said substrate retaining member as the earth electrode 2.

[0122] The interval between the earth electrode 2 (the glass plate) and the high frequency power application electrode 3 which are mutually opposed through the reaction space 12 was made to be 10 mm. The position of the impedance matching equipment 7 was adjusted to and fixed at a position where the emission intensity of plasma generated in the reaction space 12 becomes maximum.

[0123] The formation of said amorphous silicon film on said 7059 glass plate was performed as will be described below.

[0124] The inside of the reaction space 12 was evacuated to less than 0.1 Pa. After this, Ar gas was introduced into the reaction space through the spouting holes 13 of the high frequency power application electrode 3, and the inner pressure (the gas pressure) in the reaction space 12 was adjusted to and maintained at 133 Pa. Then, the 7059 glass plate was heated to and maintained at 200° C. by means of the heater 4. Thereafter, the introduction of the Ar gas into the reaction space 2 was terminated, followed by introducing SiH₄ gas and H₂ gas into the reaction space 12 at respective flow rates of 1000 sccm and 1000 sccm, and the inner pressure (the gas pressure) in the reaction space 12 was adjusted to and maintained at 266 Pa. Then, a VHF power with a frequency of 60 MHz having a wattage of 3 KW was supplied to the high frequency power application electrode 3, followed by being supplied into the reaction space 12, whereby a plasma was generated in the reaction space to cause film formation on the 7059 glass plate. This operation was continued for 5 minutes, whereby an amorphous silicon film was formed on the 7059 glass plate.

[0125] For the amorphous silicon film thus formed on the 7059 glass plate, the thicknesses at 21 positions thereof which are corresponding to prescribed 21 positions of the face (which is exposed to the reaction space 12) of the high frequency power application electrode 3 in the longitudinal direction were measured. Based on the film thicknesses measured in this way, film deposition rates at said 21 positions were computed. The computed film deposition rates are graphically shown in FIG. 10, where three film deposition rate distribution curves are established as shown in FIG. 10.

[0126] In FIG. 10, the axis of abscissas (X) indicates positions of the high frequency power application electrode 3 in the longitudinal direction and the axis of ordinates (Y) indicates film deposition rates at prescribed positions of the substrate in the width direction.

[0127] Based on the three film deposition rate distribution curves in FIG. 10, it was found that the film deposition rate distributions are of a variation of ±8% which is satisfactory.

[0128] Separately, based on the film deposition rates at the 21 positions, an average film deposition rate was computed. As a result, the average film deposition rate was found to be 67 Å/sec which is satisfactory.

[0129] The above results indicates that a deposited film can be formed over a large area at a substantially uniform thickness and at a satisfactorily high deposition rate.

[0130] Separately, neither overheat at the power introduction portion of the high frequency power application electrode nor abnormal discharge were occurred during the film formation.

COMPARATIVE EXAMPLE 1

[0131] In this comparative example, using a modification of the plasma-processing apparatus shown in FIG. 2 in that one of the two impedance matching equipments is omitted and in accordance with the film-forming procedures in Example 3, an amorphous silicon film was formed on a 7059 glass plate.

[0132] For the amorphous silicon film thus formed on the 7059 glass plate, the thicknesses at 21 positions thereof which are corresponding to prescribed 21 positions of the face (which is exposed to the reaction space 12) of the high frequency power application electrode 3 in the longitudinal direction were measured. Based on the film thicknesses measured in this way, film deposition rates at said 21 positions were computed. The computed film deposition rates are graphically shown in FIG. 11, where three film deposition rate distribution curves are established as shown in FIG. 11.

[0133] In FIG. 11, the axis of abscissas (X) indicates positions of the high frequency power application electrode 3 in the longitudinal direction and the axis of ordinates (Y) indicates film deposition rates at prescribed positions of the substrate in the width direction.

[0134] Based on the three film deposition rate distribution curves, it was found that the film deposition rate distributions are of a variation of ±45% which is apparently inferior to that (±8%) in Example 3.

[0135] Separately, based on the film deposition rates at the 21 positions, an average film deposition rate was computed. As a result, the average film deposition rate was found to be 56 Å/sec which is apparently inferior to that (67 Å/sec) in Example 3.

[0136] As described in the above, the plasma-processing apparatus of the present invention has significant advantages such that a uniform VHF plasma is stably and continuously generated such that it is uniformly distributed in the entire region of the reaction space at a uniform density and because of this, a high quality deposited film such as a non-crystalline silicon deposited film or a crystalline silicon deposited film which is free of defect is formed over the entire surface of a large area substrate at a uniform thickness and at a satisfactorily high deposition rate. 

What is claimed is:
 1. A plasma-processing apparatus comprising a vacuum vessel having a reaction space formed between a high frequency power application electrode and an earth electrode which are arranged in said vacuum vessel such that they are opposed to each other, said high frequency power application electrode having a face exposed to said reaction space, wherein a VHF power is supplied to said high frequency power application electrode to generate a plasma in said reaction space, characterized in that between other face of said high frequency power application electrode excluding said face thereof exposed to said reaction space and a conductor with earth potential comprising at least part of the circumferential wall of said vacuum vessel, an impedance matching equipment comprising a capacitive element and an inductive element which are mutually connected in series connection is arranged such that said capacitive element and said inductive element of said impedance matching equipment are symmetrical to the center of said high frequency power application electrode.
 2. The plasma-processing apparatus according to claim 1, wherein the side of the rear face of said high frequency power application electrode is exposed to an atmosphere of atmospheric pressure, and between the rear face of said high frequency power application electrode and said conductor which is situated in said atmosphere of atmospheric pressure, said impedance matching equipment is arranged in series.
 3. The plasma-processing apparatus according to claim 1, wherein said impedance matching equipment is made such that it is capable of moving in parallel to said high frequency power application electrode.
 4. The plasma-processing apparatus according to claim 2, wherein said impedance matching equipment is made such that it is capable of moving in parallel to said high frequency power application electrode.
 5. The plasma-processing apparatus according to claim 1, wherein said impedance matching equipment comprises a plurality of impedance matching equipments.
 6. The plasma-processing apparatus according to claim 2, wherein said impedance matching equipment comprises a plurality of impedance matching equipments.
 7. The plasma-processing apparatus according to claim 3, wherein said impedance matching equipment comprises a plurality of impedance matching equipments.
 8. The plasma-processing apparatus according to claim 4, wherein said impedance matching equipment comprises a plurality of impedance matching equipments. 